JP6468177B2 - Evaluation method of fine aggregate for high durability concrete - Google Patents
Evaluation method of fine aggregate for high durability concrete Download PDFInfo
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- JP6468177B2 JP6468177B2 JP2015242333A JP2015242333A JP6468177B2 JP 6468177 B2 JP6468177 B2 JP 6468177B2 JP 2015242333 A JP2015242333 A JP 2015242333A JP 2015242333 A JP2015242333 A JP 2015242333A JP 6468177 B2 JP6468177 B2 JP 6468177B2
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- 238000011156 evaluation Methods 0.000 title claims description 43
- 238000012360 testing method Methods 0.000 claims description 169
- 239000004570 mortar (masonry) Substances 0.000 claims description 119
- 239000002893 slag Substances 0.000 claims description 68
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 54
- 238000007710 freezing Methods 0.000 claims description 47
- 230000008014 freezing Effects 0.000 claims description 46
- 238000000034 method Methods 0.000 claims description 45
- 239000007864 aqueous solution Substances 0.000 claims description 42
- 235000002639 sodium chloride Nutrition 0.000 claims description 33
- 238000010257 thawing Methods 0.000 claims description 32
- 239000011780 sodium chloride Substances 0.000 claims description 27
- 239000003795 chemical substances by application Substances 0.000 claims description 21
- 230000008569 process Effects 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 7
- 238000000227 grinding Methods 0.000 claims description 7
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 claims description 6
- 239000002577 cryoprotective agent Substances 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 5
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims description 3
- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 claims description 3
- 239000001110 calcium chloride Substances 0.000 claims description 3
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 3
- 235000011148 calcium chloride Nutrition 0.000 claims description 3
- 239000001103 potassium chloride Substances 0.000 claims description 3
- 235000011164 potassium chloride Nutrition 0.000 claims description 3
- 239000001632 sodium acetate Substances 0.000 claims description 3
- 235000017281 sodium acetate Nutrition 0.000 claims description 3
- 210000000988 bone and bone Anatomy 0.000 claims description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 15
- 230000006866 deterioration Effects 0.000 description 13
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 8
- 239000000243 solution Substances 0.000 description 8
- 238000010998 test method Methods 0.000 description 8
- 230000008018 melting Effects 0.000 description 7
- 238000002844 melting Methods 0.000 description 7
- 238000010298 pulverizing process Methods 0.000 description 7
- 150000003839 salts Chemical class 0.000 description 7
- 239000004576 sand Substances 0.000 description 7
- 239000004568 cement Substances 0.000 description 6
- 239000000047 product Substances 0.000 description 6
- 239000007798 antifreeze agent Substances 0.000 description 5
- 239000013505 freshwater Substances 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- 239000002904 solvent Substances 0.000 description 5
- 238000012424 Freeze-thaw process Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 230000002528 anti-freeze Effects 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 230000008859 change Effects 0.000 description 2
- 239000012153 distilled water Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 206010060904 Freezing phenomenon Diseases 0.000 description 1
- 229910000805 Pig iron Inorganic materials 0.000 description 1
- 239000011398 Portland cement Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000007605 air drying Methods 0.000 description 1
- 239000011400 blast furnace cement Substances 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000000280 densification Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000005469 granulation Methods 0.000 description 1
- 230000003179 granulation Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 238000011417 postcuring Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 229910021487 silica fume Inorganic materials 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 210000001519 tissue Anatomy 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
Description
本発明は、凍結現象やソルトスケーリングが発生しやすい場所に適した高耐久性コンクリートを得るために、対象とする高炉スラグ細骨材が高耐久性コンクリート用細骨材としての適性を有するか否かを評価するための評価方法に関する。 Whether or not the target blast furnace slag fine aggregate is suitable as a fine aggregate for high durability concrete in order to obtain a high durability concrete suitable for a place where freezing phenomenon or salt scaling is likely to occur. The present invention relates to an evaluation method for evaluating the above.
近年、山間部や北部地域のような冬期に寒冷になる地域において、コンクリートやモルタルの早期劣化や土砂化といった問題が顕在化しつつある。冬期は、気温の低下や降雪によってコンクリートやモルタル内部に含まれる水分が凍結し、この凍結による膨張圧が発生して組織を破壊する一般的な凍害現象が起こる。これに加えて、道路等においては、人や自動車の通行の安全を確保するために凍結防止剤を散布することが広く行われているが、この凍結防止剤がコンクリートやモルタルの内部に入り込むことによって、塩害による劣化（スケーリング）が複合化し、コンクリートやモルタルの劣化を促進することが判ってきた。このように劣化したコンクリート構造物に対して、車両の通行などによる載荷が加わることで、上述したような早期劣化や土砂化が起こるものと考えられている。 In recent years, problems such as early deterioration and sedimentation of concrete and mortar are becoming apparent in areas such as mountainous areas and northern areas that are cold in winter. In winter, the moisture contained in concrete and mortar freezes due to a decrease in temperature and snowfall, and a general frost damage phenomenon occurs in which expansion pressure is generated by this freezing and destroys the tissue. In addition to this, antifreezing agents are widely sprayed on roads, etc. to ensure the safety of traffic for people and cars, but this antifreezing agent can enter concrete and mortar. It has been found that deterioration due to salt damage (scaling) is combined to promote deterioration of concrete and mortar. It is thought that the above-described premature deterioration and sedimentation occur as a result of loading of the concrete structure thus deteriorated due to vehicle traffic.
凍害を防止する方法として、コンクリート中に微細な空気を導入することが一般的に行われている。しかし、空気を導入したコンクリートは強度が低下するため、所定の強度を確保するためには、通常よりもセメントを多く配合する必要がある。このため、空気を導入する薬剤（ＡＥ剤）とセメント増量によって、原材料費が大きく増加するという問題がある。加えて、最近の研究では、蒸気養生をしたコンクリートにおいては、ＡＥ剤があまり有効に機能しないという知見も得られており、一般に蒸気養生を行って製造されるコンクリート二次製品での品質向上が必要となっている。 As a method for preventing frost damage, it is a common practice to introduce fine air into concrete. However, since the strength of the concrete introduced with air decreases, it is necessary to add more cement than usual in order to ensure a predetermined strength. For this reason, there is a problem that the cost of raw materials increases greatly due to the agent (AE agent) for introducing air and the increase in cement. In addition, recent research has also shown that AE agents do not function very effectively in steam-cured concrete, and generally improve the quality of secondary concrete products produced by steam curing. It is necessary.
これに対して、既往の研究において、高炉スラグ細骨材や高炉スラグ微粉末を配合したコンクリートは、凍結融解抵抗性および耐塩害性に優れるという知見が得られている（特許文献１、２）。このメカニズムは完全には明確になっていないが、高炉スラグ細骨材を使用することによって、骨材界面などの緻密化が起こり、界面での水の凝固による膨張・収縮や塩化物イオンの浸透を抑制するものと考えられている。 On the other hand, in past studies, it has been found that concrete blended with blast furnace slag fine aggregate or blast furnace slag fine powder is excellent in freeze-thaw resistance and salt damage resistance (Patent Documents 1 and 2). . Although this mechanism has not been fully clarified, the use of blast furnace slag fine aggregate causes densification of the aggregate interface and the like. It is thought that it suppresses.
高炉スラグ細骨材は、ＪＩＳ Ａ５０１１−１：２０１３「コンクリート用スラグ骨材 第１部 高炉スラグ骨材」で規格される工業製品であり、高炉（溶鉱炉）で銑鉄を製造する際に副産物として発生する高炉スラグのうち、溶融状態の高炉スラグに水を散布し、急速に冷却して砂状にした高炉水砕スラグを原料とし、この高炉水砕スラグを磨砕、整粒して粒の形や粒度を調整し、必要に応じて固結防止剤を散布することで製造される。高炉スラグ細骨材は、工業製品であるため、一般的な細骨材用材料としての物理的な特性は、天然材料と較べても比較的安定しているとみなすことができ、このためコンクリートやモルタルの細骨材として汎用的に用いられている。 Blast furnace slag fine aggregate is an industrial product standardized by JIS A5011-1: 2013 "Concrete slag aggregate Part 1 Blast furnace slag aggregate", and is generated as a by-product when producing pig iron in the blast furnace (blast furnace) Of the blast furnace slag to be melted, water is sprayed on the molten blast furnace slag, and the ground granulated blast furnace slag is rapidly cooled and sanded. It is manufactured by adjusting the particle size and spraying an anti-caking agent as necessary. Since blast furnace slag fine aggregate is an industrial product, its physical properties as a general fine aggregate material can be considered to be relatively stable compared to natural materials. It is widely used as a fine aggregate for mortar and mortar.
高炉スラグ細骨材を使用することにより凍害に対するコンクリートの耐久性が高まる理由については、未だ完全には解明されていないが、天然砂の細骨材を用いた場合には特性が悪く、高炉スラグ細骨材を用いた場合に優れた特性が得られるということから、粒度などの物理的な性状だけではなく、高炉スラグ細骨材がもつ何らかの化学的な寄与があると考えられる。しかしながら、製鉄所ごとの製造条件や高炉に用いる原料ソースなどの違いによって、高炉スラグ細骨材の化学的な挙動などは異なってくると考えられる。
本発明者らが、実際に様々な高炉スラグ細骨材を用いたコンクリートについて、その凍結融解特性を試験してみた結果でも、全体として耐久性の改善傾向は認められるものの、骨材によってその効果の程度に違いがあるなど、品質管理が必要であることが判った。
The reason why the durability of concrete against frost damage is increased by using blast furnace slag fine aggregate has not yet been fully elucidated, but when using fine aggregate of natural sand, the characteristics are poor and blast furnace slag Since excellent characteristics can be obtained when fine aggregate is used, it is considered that there is some chemical contribution of blast furnace slag fine aggregate as well as physical properties such as particle size. However, the chemical behavior of blast furnace slag fine aggregates will differ depending on the manufacturing conditions of each steelworks and the difference in the raw material source used in the blast furnace.
Even though the present inventors actually tested the freeze-thaw characteristics of concrete using various blast furnace slag fine aggregates, the improvement in durability as a whole was recognized, but the effect was dependent on the aggregate. It was found that quality control is necessary, for example, with different levels.
しかし、現在の耐凍害性の最も一般的な評価方法は、ＪＩＳ Ａ１１４８：２０１０「コンクリートの凍結融解試験方法」であるが、この試験方法では、１００ｍｍ×１００ｍｍ×４００ｍｍのコンクリート供試体を製造し、これを２８日養生した上で、３００サイクルの凍結融解のサイクルをかける必要がある。このため、骨材としての可否を評価するのに２ヶ月程度かかってしまい、速やかに利用したい場合などに、耐凍害性に対して有効な材料かどうかの判断が間に合わない、という問題が生じる。 However, the most common evaluation method of the current frost resistance is JIS A1148: 2010 “Freezing and thawing test method of concrete”. In this test method, a concrete specimen of 100 mm × 100 mm × 400 mm is manufactured, It is necessary to apply 300 cycles of freeze-thaw cycles after curing for 28 days. For this reason, it takes about two months to evaluate the availability as an aggregate, and there arises a problem that it is not possible to make a judgment as to whether or not the material is effective against frost resistance when it is desired to use it quickly.
したがって本発明の目的は、対象とする高炉スラグ細骨材が高耐久性コンクリート用細骨材としての適性を有するか否かを簡便且つ短期間に評価することができ、これにより、最適な高炉スラグ細骨材を速やかに選定し、凍結現象やソルトスケーリングが発生しやすい場所に適した高耐久性コンクリートを得ることを可能とする、高耐久性コンクリート用細骨材の評価方法を提供することにある。 Therefore, an object of the present invention is to easily and quickly evaluate whether or not the target blast furnace slag fine aggregate has suitability as a high durability concrete fine aggregate. To provide a method for evaluating fine aggregates for high-durability concrete, which makes it possible to quickly select slag fine aggregates and obtain high-durability concrete suitable for places where freezing and salt scaling are likely to occur. It is in.
本発明者らは、上記課題を解決できる評価方法について、実験と検討を重ねた結果、評価用サンプルの構成とサイズ、凍結融解試験の条件を最適化することにより、対象とする高炉スラグ細骨材が高耐久性コンクリート用細骨材としての適性を有するか否かを簡便且つ短期間に評価できることを見出した。
細骨材による複合劣化の挙動を明確に見極めるためには、細骨材の挙動を再現する必要がある。それと同時に、速やかな塩害の影響を受ける凍害条件も試験に反映する必要がある。それらの点から、粗骨材が入っているＪＩＳの条件では、粗骨材、細骨材、ペーストの部分の分布によって、見かけ上の初期のばらつきが大きくなり、短時間で簡便に再現することは難しい。この点について検討した結果、細骨材とペーストの部分だけで構成されるモルタルの条件にすれば、比較的簡便に安定したデータが得られる可能性が高いことが判った。
As a result of repeated experiments and studies on the evaluation method that can solve the above-mentioned problems, the present inventors have optimized the configuration and size of the sample for evaluation and the conditions of the freeze-thaw test, thereby making the target blast furnace slag fine bone It has been found that whether a material has suitability as a fine aggregate for high durability concrete can be evaluated easily and in a short time.
It is necessary to reproduce the behavior of fine aggregates in order to clearly determine the behavior of complex degradation due to fine aggregates. At the same time, frost damage conditions that are immediately affected by salt damage need to be reflected in the test. From these points, under JIS conditions that contain coarse aggregates, the initial initial variation will increase due to the distribution of coarse aggregates, fine aggregates, and paste parts, and it should be easily reproduced in a short time. Is difficult. As a result of examining this point, it has been found that if the mortar is composed of only the fine aggregate and the paste, it is highly likely that stable data can be obtained relatively easily.
また、モルタルの試験片のサイズとしては、高炉スラグ細骨材は平均粒径が２ｍｍ前後であるため、このサイズの４倍以上を確保すれば代表性は確保されること、ただし、そのサイズにモルタルを直接成形した試験片と、モルタルから切り出した試験片（切断片）とでは、初期の破壊挙動がやや異なることが判った。これについてさらに検討した結果、切断面や研削面を有する試験片を用い、骨材−ペースト界面を直接的に溶媒に接触させることが安定した評価に有効であるとの知見を得た。
本発明は、以上のような知見に基づきなされたもので、以下を要旨とするものである。
As for the size of the mortar specimen, the average particle size of the blast furnace slag fine aggregate is around 2 mm. Therefore, the representativeness can be ensured by securing at least four times this size. It was found that the initial fracture behavior was slightly different between a test piece directly molded from mortar and a test piece cut from the mortar (cut piece). As a result of further investigation, it was found that using a test piece having a cut surface or a ground surface, contacting the aggregate-paste interface directly with a solvent is effective for stable evaluation.
The present invention has been made on the basis of the above-described findings and has the following gist.
［1］評価対象となる高炉スラグ細骨材を用いて作成し、７〜２８日間水中養生したモルタルを、一辺が８〜２０ｍｍの大きさの試験片とし、
該試験片を凍結防止剤の水溶液に浸漬させた状態で、−１５℃以下の凍結工程と５℃以上の融解工程を１サイクルとする凍結融解を複数サイクル行う凍結融解試験に供し、該凍結融解試験後に塊として残存しているモルタルの割合から、高耐久性コンクリート用骨材としての当該高炉スラグ細骨材の適性を評価することを特徴とする高耐久性コンクリート用細骨材の評価方法。
[1] A mortar made with blast furnace slag fine aggregate to be evaluated and cured under water for 7 to 28 days is used as a test piece having a side of 8 to 20 mm in size.
In a state where the test piece is immersed in an aqueous solution of an antifreezing agent, the sample is subjected to a freeze-thaw test in which a freeze-thaw is performed in a plurality of cycles with a freezing step of −15 ° C. or lower and a thawing step of 5 ° C. or higher as one cycle. A method for evaluating a fine aggregate for high durability concrete, characterized by evaluating the suitability of the blast furnace slag fine aggregate as a high durability concrete aggregate from the ratio of mortar remaining as a lump after the test.
［2］評価対象となる高炉スラグ細骨材を用いて作成し、蒸気養生したモルタルを、一辺が８〜２０ｍｍの大きさの試験片とし、
該試験片を凍結防止剤の水溶液に浸漬させた状態で、−１５℃以下の凍結工程と５℃以上の融解工程を１サイクルとする凍結融解を複数サイクル行う凍結融解試験に供し、該凍結融解試験後に塊として残存しているモルタルの割合から、高耐久性コンクリート用骨材としての当該高炉スラグ細骨材の適性を評価することを特徴とする高耐久性コンクリート用細骨材の評価方法。
[2] Using a blast furnace slag fine aggregate to be evaluated and steam-cured mortar as a test piece having a side of 8 to 20 mm,
In a state where the test piece is immersed in an aqueous solution of an antifreezing agent, the sample is subjected to a freeze-thaw test in which a freeze-thaw is performed in a plurality of cycles with a freezing step of −15 ° C. or lower and a thawing step of 5 ° C. or higher as one cycle. A method for evaluating a fine aggregate for high durability concrete, characterized by evaluating the suitability of the blast furnace slag fine aggregate as a high durability concrete aggregate from the ratio of mortar remaining as a lump after the test.
［3］上記［1］または［2］の評価方法において、試験片は、養生後のモルタルから切り出された切断片または養生後のモルタルの表面を研削した研削片であることを特徴とする高耐久性コンクリート用細骨材の評価方法。
［4］上記［1］〜［3］のいずれかの評価方法において、試験片を浸漬させる水溶液は、凍結防止剤として、塩化ナトリウム、塩化カリウム、塩化カルシウム、酢酸ナトリウムの中から選ばれる１種以上を含有することを特徴とする高耐久性コンクリート用細骨材の評価方法。
［5］上記［4］の評価方法において、試験片を浸漬させる水溶液は、凍結防止剤として塩化ナトリウムを含有することを特徴とする高耐久性コンクリート用細骨材の評価方法。
[3] In the evaluation method of [1] or [2] above, the test piece is a cut piece cut out from the mortar after curing or a ground piece obtained by grinding the surface of the mortar after curing. Evaluation method of durable fine aggregate for concrete.
[4] In the evaluation method according to any one of [1] to [3], the aqueous solution in which the test piece is immersed is one kind selected from sodium chloride, potassium chloride, calcium chloride, and sodium acetate as an antifreeze agent. The evaluation method of the fine aggregate for highly durable concrete characterized by containing the above.
[5] In the evaluation method of [4], the aqueous solution in which the test piece is immersed contains sodium chloride as an antifreezing agent.
［6］上記［1］〜［5］のいずれかの評価方法において、試験片を浸漬させる水溶液中の凍結防止剤の濃度が０．５〜１０質量％であることを特徴とする高耐久性コンクリート用細骨材の評価方法。
［7］上記［1］〜［6］のいずれかの評価方法において、凍結融解試験では、凍結工程の時間（但し、温度降下中の時間と保持時間の合計）と融解工程の時間（但し、温度上昇中の時間と保持時間の合計）の合計を１サイクルあたり２４時間以内とし、且つ凍結工程の時間（但し、温度降下中の時間と保持時間の合計）と融解工程の時間（但し、温度上昇中の時間と保持時間の合計）を、それぞれ１サイクルあたり４時間以上とすることを特徴とする高耐久性コンクリート用細骨材の評価方法。
[6] In the evaluation method according to any one of [1] to [5] above, the durability of the antifreeze in the aqueous solution in which the test piece is immersed is 0.5 to 10% by mass Evaluation method for fine aggregate for concrete.
[7] In the evaluation method according to any one of [1] to [6] above, in the freeze-thaw test, the time of the freezing step (however, the total of the time during the temperature drop and the holding time) and the time of the thawing step (however, The total of the time during the temperature rise and the retention time is within 24 hours per cycle, and the time for the freezing step (however, the total time during the temperature drop and the retention time) and the time for the thawing step (however, the temperature A method for evaluating fine aggregates for high durability concrete, characterized in that the total of the rising time and the holding time is 4 hours or more per cycle.
［8］上記［1］〜［7］のいずれかの評価方法において、凍結融解試験後のモルタルを篩目が０．６〜２．５ｍｍの篩で分級し、その篩上を塊として残存しているモルタルとし、その質量を測定することを特徴とする高耐久性コンクリート用細骨材の評価方法。
［9］上記［1］〜［8］のいずれかの評価方法において、凍結融解試験において、凍結融解を５サイクル以上行うことを特徴とする高耐久性コンクリート用細骨材の評価方法。
［10］上記［1］〜［9］のいずれかの評価方法において、モルタルを養生した後、試験片を凍結防止剤の水溶液に浸漬させるまでの間に、乾燥工程を経ないことを特徴とする高耐久性コンクリート用細骨材の評価方法。
[8] In the evaluation method according to any one of [1] to [7] above, the mortar after the freeze-thaw test is classified with a sieve having a sieve mesh of 0.6 to 2.5 mm, and the sieve remains as a lump. The evaluation method of the fine aggregate for highly durable concrete characterized by measuring the mass.
[9] A method for evaluating a high-durability concrete fine aggregate, wherein the freeze-thawing is performed for 5 cycles or more in the freeze-thaw test in the evaluation method according to any one of [1] to [8].
[10] The method according to any one of [1] to [9] above, wherein the drying step is not performed after the mortar is cured and before the test piece is immersed in the aqueous solution of the antifreeze agent. To evaluate fine aggregate for high durability concrete.
本発明の評価方法によれば、対象とする高炉スラグ細骨材が高耐久性コンクリート用細骨材としての適性を有するか否かを簡便且つ短期間に評価することができる。このため、最適な高炉スラグ細骨材を速やかに選定し、凍結現象やソルトスケーリングが発生しやすい場所に適した高耐久性コンクリートを製造することができる。 According to the evaluation method of the present invention, it is possible to easily and quickly evaluate whether or not the target blast furnace slag fine aggregate is suitable as a high durability concrete fine aggregate. For this reason, the optimum blast furnace slag fine aggregate can be quickly selected, and highly durable concrete suitable for a place where freezing and salt scaling are likely to occur can be manufactured.
本発明法は、高炉スラグ細骨材について、高耐久性コンクリート用骨材としての適性を有するか否かを評価するための評価方法であり、評価対象となる高炉スラグ細骨材を用いて作成し、所定の養生を施したモルタルを所定の大きさの試験片とし、この試験片を凍結防止剤の水溶液に浸漬させた状態で、所定条件の凍結融解試験に供し、この凍結融解試験後に塊として残存しているモルタルの割合（塊状部の残存率）から、高耐久性コンクリート用細骨材としての当該高炉スラグ細骨材の適性を評価するものである。
ここで、高耐久性コンクリートとは、コンクリート供試体に対するＪＩＳ Ａ１１４８：２０１０「コンクリートの凍結融解試験方法」に記載のＡ法に基づく凍結融解試験における凍結融解サイクル３００回での相対動弾性係数が６０％以上であるようなコンクリートを指す。
The method of the present invention is an evaluation method for evaluating whether or not a blast furnace slag fine aggregate has suitability as a high durability concrete aggregate, and is prepared using a blast furnace slag fine aggregate to be evaluated. Then, a mortar subjected to a predetermined curing is used as a test piece of a predetermined size, and the test piece is immersed in an aqueous solution of a cryoprotectant and subjected to a freeze-thaw test under predetermined conditions. From the ratio of the remaining mortar (remaining ratio of the massive portion), the suitability of the blast furnace slag fine aggregate as a fine aggregate for high durability concrete is evaluated.
Here, the high durability concrete has a relative dynamic elastic modulus of 60 in a freeze-thaw cycle in a freeze-thaw test in a freeze-thaw test based on the method A described in JIS A1148: 2010 “Concrete Freeze-Thaw Test Method” for concrete specimens. Percent concrete.
高炉スラグ細骨材の影響を明確に評価するために、マトリックスとの相互関係を再現して耐久性を評価することが必要であるため、本発明法では、評価対象とする高炉スラグ細骨材を用いたモルタルを作成して評価を行う。さきに述べたように、粗骨材が入っているＪＩＳ（ＪＩＳ Ａ１１４８：２０１０「コンクリートの凍結融解試験方法」）の条件では、粗骨材、細骨材、ペーストの部分の分布によって、見かけ上の初期のばらつきが大きくなり、短時間で簡便に再現することは難しい。これに対して、細骨材とペーストの部分だけで構成されるモルタルの条件にすれば、比較的簡便に安定したデータが得られる可能性が高い。 In order to clearly evaluate the influence of blast furnace slag fine aggregate, it is necessary to reproduce the interrelationship with the matrix and evaluate the durability. Therefore, in the method of the present invention, the blast furnace slag fine aggregate to be evaluated is used. Make a mortar using and evaluate it. As described above, under the conditions of JIS (JIS A1148: 2010 “Concrete Freezing and Thawing Test Method”) in which coarse aggregate is contained, the apparent distribution depends on the distribution of coarse aggregate, fine aggregate, and paste. The initial variation of the image becomes large, and it is difficult to easily reproduce in a short time. On the other hand, if the mortar is composed of only fine aggregate and paste, it is highly possible that stable data can be obtained relatively easily.
モルタルの配合条件は特に限定しないが、例えば、ＪＩＳ Ａ１１４６：２００７「骨材のアルカリシリカ反応性試験方法（モルタルバー法）」に記載の配合条件、あるいはコンクリートを製造する条件で粗骨材を取り除いた配合条件、などを用いればよい。
モルタルに用いるセメントの種類は特に制限はなく、普通ポルトランドセメント、早強セメント、高炉セメント、シリカフュームセメントなどの１種以上を用いることができる。
Mortar blending conditions are not particularly limited. For example, coarse aggregates are removed under the blending conditions described in JIS A1146: 2007 “Aggregate Alkali-Silica Reactivity Test Method (mortar bar method)” or concrete production conditions. The blending conditions may be used.
There is no restriction | limiting in particular in the kind of cement used for mortar, One or more types, such as normal Portland cement, early-strength cement, blast furnace cement, silica fume cement, can be used.
モルタルは、所定条件で養生した後に評価に用いる。モルタルの養生条件は、基本的に適用しようとするコンクリート製品と同じような条件にし、養生後の評価を行うのが望ましい。具体的には、コンクリートで標準養生と呼ばれる、２０℃の水中で２８日間養生したものを評価するのが最も望ましいが、現場養生での実際の温度条件に合わせた養生を実施したものを評価することも可能である。水中で養生する場合、より短期間での評価も可能であるが、ペースト部分の内部組織を安定にさせるため、７日以上養生したのちに評価することが望ましい。また、コンクリート二次製品のように、打ち込み後に蒸気養生して製品を製造するような場合には、本発明法のモルタルについても同じように蒸気で促進養生したものを評価に供することも可能である。
したがって、本発明では、評価対象となる高炉スラグ細骨材を用いて作成し、７〜２８日間（材齢７日以上２８日以下の間）水中養生したモルタル、または蒸気養生したモルタルを評価対象にする。水中養生については、ＪＩＳ Ｒ５２０１：１９９７「セメントの物理試験方法」に規定される２０℃±１℃が望ましい。蒸気養生については、各工場で製造する過程を模擬した条件が望ましい。
Mortar is used for evaluation after curing under predetermined conditions. It is desirable that the mortar curing conditions are basically the same as the concrete products to be applied, and the post-curing evaluation is performed. Specifically, it is most desirable to evaluate concrete that has been cured for 28 days in water at 20 ° C, which is called standard curing, but it is to evaluate what has been cured according to actual temperature conditions in field curing. It is also possible. When curing in water, evaluation in a shorter period is possible, but it is desirable to evaluate after curing for 7 days or more in order to stabilize the internal structure of the paste part. In addition, in the case of producing a product by steam curing after placing, such as a concrete secondary product, the mortar of the method of the present invention can also be used for evaluation with steam accelerated curing similarly. is there.
Therefore, in the present invention, a mortar prepared using blast furnace slag fine aggregate to be evaluated and cured under water for 7 to 28 days (between age 7 and 28), or steam-cured mortar is evaluated. To. For underwater curing, 20 ° C. ± 1 ° C. as defined in JIS R5201: 1997 “Cement physical test method” is desirable. For steam curing, conditions that simulate the process of manufacturing at each factory are desirable.
本発明法では、上記のようにして得られるモルタルを所定の大きさの試験片（小片）とし、この試験片を凍結防止剤の水溶液に浸漬させた状態で、所定条件の凍結融解試験に供し、この凍結融解試験後に塊として残存しているモルタルの割合（塊状部の残存率）から、高耐久性コンクリート用細骨材としての当該高炉スラグ細骨材の適性を評価する。この評価方法の典型的な具体例を、参考例とともに以下に示す。
評価対象とする高炉スラグ細骨材を用い、ＪＩＳ Ａ１１４６：２００７の条件でモルタルを作成し、２８日間水中養生を施した。得られたモルタルを切断して各辺が１０ｍｍの立方体形状の試験片を切り出し、４つの試験片を１セットとして、凍結防止剤の水溶液に浸漬させた。凍結防止剤の水溶液としては、３質量％ＮａＣｌ水溶液と１０質量％ＮａＣｌ水溶液を用いた。また、参考例として、同様の試験片を真水（蒸留水）に浸漬させた。
In the method of the present invention, the mortar obtained as described above is used as a test piece (small piece) of a predetermined size, and this test piece is immersed in an aqueous solution of an antifreeze and subjected to a freeze-thaw test under predetermined conditions. The suitability of the blast furnace slag fine aggregate as a fine aggregate for high durability concrete is evaluated from the ratio of the mortar remaining as a lump after this freeze-thaw test (remaining ratio of the lump). A typical example of this evaluation method is shown below together with a reference example.
Using the blast furnace slag fine aggregate to be evaluated, mortar was prepared under the conditions of JIS A1146: 2007, and water curing was performed for 28 days. The obtained mortar was cut and a cube-shaped test piece having a side of 10 mm was cut out, and four test pieces were taken as one set and immersed in an aqueous solution of an antifreezing agent. As an aqueous solution of the cryoprotectant, a 3 mass% NaCl aqueous solution and a 10 mass% NaCl aqueous solution were used. Moreover, the same test piece was immersed in fresh water (distilled water) as a reference example.
試験片は、浸漬した液（水溶液または真水）に浸けたままの状態で、−１８℃の凍結工程と２０℃の融解工程を１サイクルとする凍結融解を複数サイクル行う凍結融解試験に供した。この凍結融解試験では、凍結工程（−１８℃）の時間（但し、温度降下中の時間と保持時間の合計）を１サイクルあたり１６時間、融解工程（２０℃）の時間（但し、温度上昇中の時間と保持時間の合計）を１サイクルあたり８時間とした。また、比較のため、山砂を細骨材に用いたモルタルの試験片を上記と同様の手法で作成した。 The test piece was subjected to a freeze-thaw test in which a plurality of cycles of freeze-thaw with one cycle of a freezing step at −18 ° C. and a thawing step at 20 ° C. were carried out in a dipped solution (aqueous solution or fresh water). In this freeze-thaw test, the time of the freezing step (−18 ° C.) (however, the total of the time during the temperature drop and the holding time) is 16 hours per cycle, and the time of the melting step (20 ° C.) (however, the temperature is rising) The total of the time and the holding time) was 8 hours per cycle. For comparison, a mortar specimen using mountain sand as fine aggregate was prepared in the same manner as described above.
高炉スラグ細骨材を用いたモルタルの試験片について、凍結融解試験（凍結融解１０サイクル）後の外観写真を図１に示す。図１の写真は、左側から順に、真水（蒸留水）に浸漬させた状態で凍結融解試験に供したもの、３質量％ＮａＣｌ水溶液に浸漬させた状態で凍結融解試験に供したもの、１０質量％ＮａＣｌ水溶液に浸漬させた状態で凍結融解試験に供したものである。これによれば、真水に浸漬させた状態で凍結融解試験に供した試験片はほとんど変化が見られず、モルタルを評価することは難しいことが判る。これに対して、ＮａＣｌ溶液に浸漬させた状態で凍結融解試験に供した試験片は、半分以上が粉化していることが確認され、促進劣化によって短期間で評価できる可能性が高いことが判る。 About the test piece of the mortar using the blast furnace slag fine aggregate, the external appearance photograph after a freezing and thawing test (freezing and thawing 10 cycles) is shown in FIG. The photographs in FIG. 1 are, in order from the left side, subjected to a freeze-thaw test in a state of being immersed in fresh water (distilled water), and subjected to a freeze-thaw test in a state of being immersed in a 3% by mass NaCl aqueous solution. The sample was subjected to a freeze-thaw test in a state of being immersed in an aqueous NaCl solution. According to this, it can be seen that the test piece subjected to the freeze-thaw test in a state immersed in fresh water hardly changes, and it is difficult to evaluate the mortar. On the other hand, it is confirmed that more than half of the test pieces subjected to the freeze-thaw test in a state immersed in a NaCl solution are pulverized, and it is highly possible that evaluation can be performed in a short period of time due to accelerated deterioration. .
３質量％ＮａＣｌ水溶液に浸漬させた試験片の凍結融解試験では、凍結融解を異なるサイクル数で行った。凍結融解試験後のモルタル（試験片）を篩目が２ｍｍの篩で分級し、その篩上を塊（塊状部）として残存しているモルタルとし（篩下を粉化したモルタルとする）、塊（塊状部）として残存しているモルタルの割合（塊状部の残存率＝（［塊として残存しているモルタルの質量］／［モルタルの全質量］）×１００）を調べた。比較のため、山砂を細骨材に用いたモルタルの試験片について、同様の試験を行った。それらの結果を図２に示す。 In the freeze-thaw test of test pieces immersed in a 3% by mass NaCl aqueous solution, freeze-thaw was performed at different number of cycles. The mortar (test piece) after the freeze-thaw test is classified with a sieve having a sieve mesh of 2 mm, and the mortar on the sieve is left as a lump (lumped portion) (the mortar below the sieve is powdered). The ratio of the mortar remaining as (lumped portion) (residual ratio of the massive portion = ([mass of mortar remaining as a mass] / [total mass of mortar]) × 100) was examined. For comparison, a similar test was performed on a mortar specimen using mountain sand as a fine aggregate. The results are shown in FIG.
図２によれば、山砂を細骨材に用いたモルタルの試験片は、凍結融解１０サイクルの時点でほとんど粉状になってしまうのに対して、高炉スラグ細骨材を用いたモルタルの試験片は、凍結融解１０サイクルの時点でも７０質量％程度が塊状のまま残存している。山砂を細骨材に用いたモルタルは、実際に凍害現象が起こっているものであり、高炉スラグ細骨材を用いたモルタルは良好な状態が維持できていたことから、以上の結果を考え合わせると、「モルタルの試験片を凍結防止剤の水溶液に浸漬させた状態で、所定条件の凍結融解を複数サイクル行う凍結融解試験に供し、該凍結融解試験後に塊として残存しているモルタルの割合を調べる」という促進劣化を利用した評価手法は、細骨材の適性評価には有効であることが示唆される。 According to FIG. 2, mortar specimens using pile sand as fine aggregates are almost powdered at the time of 10 cycles of freezing and thawing, whereas mortar specimens using blast furnace slag fine aggregates. About 70% by mass of the test piece remains in a lump even after 10 cycles of freezing and thawing. Mortars using mountain sand as fine aggregates are actually frost damage phenomena, and mortars using blast furnace slag fine aggregates maintained good conditions. In combination, the ratio of the mortar remaining as a lump after the freeze-thaw test is subjected to a freeze-thaw test in which a mortar specimen is immersed in an aqueous solution of an antifreeze agent and subjected to freeze-thaw cycles of a predetermined condition. It is suggested that the evaluation method using accelerated deterioration called “investigation” is effective in evaluating the suitability of fine aggregates.
以上のように、促進劣化を利用した評価手法は、高炉スラグ細骨材の適性評価に活用できると考えられるが、実際に使用するには、安定した評価ができることが必要となる。そのために必要な試験条件は、以下のとおりである。
まず、モルタルの試験片の大きさは、一辺が８〜２０ｍｍの小片とする。高炉スラグ細骨材の平均粒径は２ｍｍ前後であるため、試験片の一辺が８ｍｍ未満では、骨材のモルタル内の存在確率が不安定になり、データの安定性が低下する。一方、試験片のサイズは大きくても評価は可能であるが、全体の質量に対する粉化割合が低下するため、データの判定精度が低下してしまう。一辺が２０ｍｍ以下の大きさとすることで、凍結融解５〜１０サイクル程度で明確な粉化率の質量変化を把握することが可能となる。
なお、試験片の形状は、一般に直方体または立方体である。
As described above, it is considered that the evaluation method using accelerated deterioration can be used for evaluating the suitability of blast furnace slag fine aggregate. However, in order to actually use it, it is necessary to be able to perform stable evaluation. The test conditions necessary for this are as follows.
First, the size of the mortar test piece is a small piece having a side of 8 to 20 mm. Since the average particle size of the blast furnace slag fine aggregate is around 2 mm, if one side of the test piece is less than 8 mm, the existence probability in the mortar of the aggregate becomes unstable and the stability of the data decreases. On the other hand, evaluation is possible even if the size of the test piece is large, but since the pulverization ratio with respect to the entire mass is reduced, the data determination accuracy is reduced. By setting the size of one side to 20 mm or less, it becomes possible to grasp a clear change in mass of the powdering rate in about 5 to 10 cycles of freezing and thawing.
The shape of the test piece is generally a rectangular parallelepiped or a cube.
また、試験片は、細骨材とモルタル界面が溶媒（凍結防止剤の水溶液）に直接接触するようなものであることが望ましい。図３と図４は、凍結融解試験を経た試験片表面（研磨面）の拡大写真であり、図３は山砂を細骨材に用いたモルタルの試験片、図４は高炉スラグ細骨材を用いたモルタルの試験片である。亀裂の程度は異なるが、いずれの試験片も、細骨材とマトリックス（ペースト）の界面部分に亀裂が進展しており、これが劣化の主要因になっていることが判る。 The test piece is preferably such that the interface between the fine aggregate and the mortar is in direct contact with the solvent (an aqueous solution of an antifreezing agent). 3 and 4 are enlarged photographs of the specimen surface (polished surface) that has undergone the freeze-thaw test, FIG. 3 is a mortar specimen using mountain sand as a fine aggregate, and FIG. 4 is a blast furnace slag fine aggregate. It is a test piece of mortar using. Although the degree of cracking is different, it can be seen that cracks propagated at the interface between the fine aggregate and the matrix (paste) in all the test pieces, and this is the main cause of deterioration.
本発明法で用いる一辺が８〜２０ｍｍの大きさの試験片を得る方法としては、例えば、（i）モルタルを大きなサイズ（例えば、ＪＩＳで用いられる４０ｍｍ×４０ｍｍ×１６０ｍｍ）に成形して、そこから試験片を切り出す方法、（ii）最初からモルタルを一辺が８〜２０ｍｍの大きさに成形して試験片とする方法、などがあるが、（ii）の方法では、試験片の外表面がすべてペーストのみになってしまうため、細骨材とモルタル界面が溶媒（凍結防止剤の水溶液）に直接接触せず、僅かではあるが促進劣化を抑制する傾向になる。 As a method for obtaining a test piece having a side of 8 to 20 mm used in the method of the present invention, for example, (i) mortar is molded into a large size (for example, 40 mm × 40 mm × 160 mm used in JIS) There is a method of cutting a test piece from (ii), a method of forming a mortar from the beginning into a size of 8 to 20 mm to make a test piece, etc., but in the method of (ii), the outer surface of the test piece is Since all of the paste becomes only, the interface between the fine aggregate and the mortar is not in direct contact with the solvent (an aqueous solution of an antifreezing agent), and the tendency to suppress accelerated deterioration is slight.
したがって、本発明法で用いる試験片は、上記（ii）の方法で得られたものでもよいが、上記（i）の方法で得られたもの、すなわち、養生後のモルタルから切り出された切断片であることが好ましい。また、その場合、試験片の外表面の一部が切断面となる切断片でもよいが、外表面全体（全面）が切断面となるように切り出された切断片であることが特に望ましい。また、切断片ではなく、養生後のモルタルの表面を研削した研削片とし、細骨材とモルタル界面を溶媒に直接接触させるようにしてもよい。 Therefore, the test piece used in the method of the present invention may be obtained by the above method (ii), but is obtained by the above method (i), that is, a cut piece cut out from the mortar after curing. It is preferable that In this case, a part of the outer surface of the test piece may be a cut piece that becomes a cut surface, but a cut piece that is cut out so that the entire outer surface (entire surface) becomes a cut surface is particularly desirable. Further, instead of the cut piece, a ground piece obtained by grinding the surface of the mortar after curing may be used so that the fine aggregate and the mortar interface are brought into direct contact with the solvent.
図５は、高炉スラグ細骨材を用いたモルタルの試験片であって、上記（i）の方法で得られた試験片（モルタルから切り出された試験片）を用いた場合（Ａ〜Ｃ）と、上記（ii）の方法で得られた試験片（モルタルを直接成形して得られた試験片）を用いた場合（Ｄ）について、図２と同様の方法で、凍結融解試験後に塊（塊状部）として残存しているモルタルの割合（塊状部の残存率）を調べた結果を示している。各試験片のモルタルは、高炉スラグ細骨材を用いてＪＩＳ Ａ１１４６：２００７の条件で作成し、２８日間水中養生を施した。試験片は各辺が１０ｍｍの立方体形状とした。この試験片を３質量％ＮａＣｌ水溶液に浸漬させた状態で、−１８℃の凍結工程と２０℃の融解工程を１サイクルとする凍結融解を複数サイクル行う凍結融解試験に供した。この凍結融解試験では、凍結融解を異なるサイクル数で行った。また、凍結工程（−１８℃）の時間（但し、温度降下中の時間と保持時間の合計）を１サイクルあたり１６時間、融解工程（２０℃）の時間（但し、温度上昇中の時間と保持時間の合計）を１サイクルあたり８時間とした。 FIG. 5 is a mortar test piece using a blast furnace slag fine aggregate, and the test piece (test piece cut out from the mortar) obtained by the method (i) is used (AC). And (D) using the test piece obtained by the above method (ii) (test piece obtained by directly molding mortar), the mass ( The result of investigating the ratio of mortar remaining as a lump portion (remaining rate of lump portion) is shown. The mortar of each test piece was prepared under the conditions of JIS A1146: 2007 using blast furnace slag fine aggregate, and was subjected to water curing for 28 days. The test piece had a cubic shape with each side of 10 mm. With this test piece immersed in a 3% by weight NaCl aqueous solution, it was subjected to a freeze-thaw test in which a freeze-thaw was performed in a plurality of cycles with a freezing step at -18 ° C and a thawing step at 20 ° C as one cycle. In this freeze-thaw test, freeze-thaw was performed at different cycle numbers. Also, the freezing step (−18 ° C.) time (however, the total of the time during the temperature drop and the holding time) is 16 hours per cycle, and the time of the melting step (20 ° C.) (however, the time during the temperature rise and holding) The total time) was 8 hours per cycle.
図５によると、上記（i）の方法で得られた試験片を用いた場合には、バラツキも小さくほぼ同じ結果になっているのに対し、上記（ii）の方法で得られた試験片を用いた場合には、促進劣化がやや遅れている結果になっている。このことから、上記（ii）の方法で得られた試験片を用いても、評価そのものは問題なくできるが、上記（i）の方法で得られた試験片を用いた方がより望ましい。 According to FIG. 5, when the test piece obtained by the method (i) is used, the variation is small and the results are almost the same, whereas the test piece obtained by the method (ii) is used. When is used, the result is that the accelerated deterioration is slightly delayed. From this, even if the test piece obtained by the method (ii) is used, the evaluation itself can be performed without any problem, but it is more preferable to use the test piece obtained by the method (i).
試験片を浸漬させる水溶液に含まれる凍結防止剤としては、実際にその地域の道路などで用いられているものを適用すればよい。具体的には、塩化ナトリウム、塩化カリウム、塩化カルシウム、酢酸ナトリウムなどが挙げられ、これらの１種以上を用いることができるが、採用している地域が最も多いこと、入手が容易であること、などの理由から塩化ナトリウムが特に好ましい。
水溶液中での凍結防止剤の濃度は、０．５〜１０質量％程度が好ましく、１〜６質量％程度がより好ましい。
What is necessary is just to apply what is actually used on the road etc. of the area as an antifreezing agent contained in the aqueous solution in which a test piece is immersed. Specifically, sodium chloride, potassium chloride, calcium chloride, sodium acetate and the like can be mentioned, and one or more of these can be used, but the most adopted areas are easy to obtain, Sodium chloride is particularly preferred for reasons such as these.
The concentration of the antifreezing agent in the aqueous solution is preferably about 0.5 to 10% by mass, and more preferably about 1 to 6% by mass.
図６は、試験片を浸漬させる水溶液中の塩化ナトリウム濃度と凍結融解試験によるモルタル（試験片）の粉化率との関係を調べた結果を示している。この試験では、高炉スラグ細骨材を用いてＪＩＳ Ａ１１４６：２００７の条件でモルタルを作成し、２８日間水中養生を施した。得られたモルタルを切断して各辺が１０ｍｍの立方体形状の試験片を切り出した。この試験片をＮａＣｌ水溶液に浸漬させた状態で、−１８℃の凍結工程と２０℃の融解工程を１サイクルとする凍結融解を１０サイクル行う凍結融解試験に供した。また、凍結工程（−１８℃）の時間（但し、温度降下中の時間と保持時間の合計）を１サイクルあたり１６時間、融解工程（２０℃）の時間（但し、温度上昇中の時間と保持時間の合計）を１サイクルあたり８時間とした。この凍結融解試験後のモルタル（試験片）を篩目が２ｍｍの篩で分級して、篩下を粉化したモルタルとし、粉化率（＝（［粉化したモルタルの質量］／［モルタルの全質量］）×１００）を調べた。 FIG. 6 shows the results of examining the relationship between the concentration of sodium chloride in the aqueous solution in which the test piece is immersed and the powdering rate of the mortar (test piece) by the freeze-thaw test. In this test, mortar was prepared using blast furnace slag fine aggregates under the conditions of JIS A1146: 2007, and was subjected to water curing for 28 days. The obtained mortar was cut and a cube-shaped test piece having a side of 10 mm was cut out. With this test piece immersed in a NaCl aqueous solution, it was subjected to a freeze-thaw test in which 10 cycles of freeze-thaw were performed with a freezing step at −18 ° C. and a melting step at 20 ° C. as one cycle. Also, the freezing step (−18 ° C.) time (however, the total of the time during the temperature drop and the holding time) is 16 hours per cycle, and the time of the melting step (20 ° C.) (however, the time during the temperature rise and holding) The total time) was 8 hours per cycle. The mortar (test piece) after this freeze-thaw test was classified with a sieve having a sieve mesh of 2 mm, and the under-sieving was pulverized mortar, and the pulverization rate (= (mass of pulverized mortar] / [mortar Total mass]) × 100) was investigated.
図６によれば、水溶液の塩化ナトリウム濃度が０．５質量％以上であれば、高い粉化率が得られ、安定した促進劣化効果が現れている。また、塩化ナトリウム濃度が１０質量％程度までは高い粉化率を示すが、１０質量％を超えると逆に低下している。また、１〜６質量％の範囲では、濃度の影響が小さく安定した粉化率となっている。以上の結果から、水溶液中の凍結防止剤（特に塩化ナトリウム）の濃度は、０．５〜１０質量％が好ましく、１〜６質量％がより好ましい。 According to FIG. 6, when the sodium chloride concentration of the aqueous solution is 0.5% by mass or more, a high pulverization rate is obtained, and a stable accelerated deterioration effect appears. Moreover, although the sodium chloride density | concentration shows a high powdering rate to about 10 mass%, when it exceeds 10 mass%, it will fall conversely. Moreover, in the range of 1 to 6% by mass, the influence of the concentration is small and the pulverization rate is stable. From the above results, the concentration of the antifreezing agent (particularly sodium chloride) in the aqueous solution is preferably 0.5 to 10% by mass, and more preferably 1 to 6% by mass.
本発明の凍結融解試験では、凍結防止剤の水溶液に浸漬させた状態の試験片に対して、−１５℃以下の凍結工程と５℃以上の融解工程を１サイクルとする凍結融解を複数サイクル行う。
図７は、凍結融解試験における凍結工程の温度および凍結融解のサイクル数と、凍結融解試験後に塊として残存しているモルタルの割合（塊状部の残存率）との関係を調べた結果を示している。この試験では、高炉スラグ細骨材を用いてＪＩＳ Ａ１１４６：２００７の条件でモルタルを作成し、２８日間水中養生を施した。得られたモルタルを切断して各辺が１０ｍｍの立方体形状の試験片を切り出した。この試験片を３質量％ＮａＣｌ水溶液に浸漬させた状態で、凍結工程と融解工程（２０℃）を１サイクルとする凍結融解を複数サイクル行う凍結融解試験に供した。この凍結融解試験では、凍結融解を異なるサイクル数と異なる凍結工程の温度で行った。また、凍結工程の時間（但し、温度降下中の時間と保持時間の合計）を１サイクルあたり１６時間、融解工程（２０℃）の時間（但し、温度上昇中の時間と保持時間の合計）を１サイクルあたり８時間とした。凍結融解試験後のモルタル（試験片）を篩目が２ｍｍの篩で分級し、その篩上を塊（塊状部）として残存しているモルタルとし、塊（塊状部）として残存しているモルタルの割合（塊状部の残存率＝（［塊として残存しているモルタルの質量］／［モルタルの全質量］）×１００）を調べた。
In the freeze-thaw test of the present invention, multiple cycles of freeze-thaw with a cycle of a freeze step of −15 ° C. or lower and a thaw step of 5 ° C. or higher are performed on a test piece immersed in an antifreeze aqueous solution. .
FIG. 7 shows the results of examining the relationship between the temperature of the freezing step and the number of cycles of freezing and thawing in the freeze-thaw test, and the ratio of mortar remaining as a lump after the freeze-thaw test (remaining ratio of the lump). Yes. In this test, mortar was prepared using blast furnace slag fine aggregates under the conditions of JIS A1146: 2007, and was subjected to water curing for 28 days. The obtained mortar was cut and a cube-shaped test piece having a side of 10 mm was cut out. With this test piece immersed in a 3% by mass NaCl aqueous solution, it was subjected to a freeze-thaw test in which freeze-thaw was performed for a plurality of cycles with the freezing step and the thawing step (20 ° C.) as one cycle. In this freeze-thaw test, freeze-thaw was performed at different cycle numbers and different freezing process temperatures. Also, the time for the freezing step (however, the sum of the time during the temperature drop and the holding time) is 16 hours per cycle, and the time for the melting step (20 ° C.) (however, the sum of the time during the temperature rise and the holding time) 8 hours per cycle. The mortar (test piece) after the freeze-thaw test is classified with a sieve having a sieve mesh of 2 mm, the mortar remaining on the sieve as a lump (lumped part), and the mortar remaining as a lump (lumpy part) The ratio (residual ratio of lump portion = ([mass of mortar remaining as a lump] / [total mass of mortar]) × 100) was examined.
図７によれば、凍結工程の温度が−５℃程度では、試験片はほとんど粉化しない。これは、凍結防止剤の凝固点を降下させる作用が働くことによって、凍結が起こらないためである。一方、−１０℃程度で粉化が起こることが確認されるが、−１５℃以下にすることによって粉化（促進劣化）の度合いが安定することが判る。このため凍結工程の温度は−１５℃以下とする。
また、融解工程の温度については、上記のように−５℃以上であれば凍結防止剤の水溶液は液体化するが、確実に液体とするために５℃以上とする。また、好ましくは１０℃以上とし、特に好ましくは２０℃程度とするのが望ましい。
According to FIG. 7, when the temperature in the freezing step is about −5 ° C., the test piece is hardly powdered. This is because freezing does not occur due to the action of lowering the freezing point of the cryoprotectant. On the other hand, although it is confirmed that pulverization occurs at about −10 ° C., it is understood that the degree of pulverization (accelerated deterioration) is stabilized by setting the temperature to −15 ° C. or lower. For this reason, the temperature of a freezing process shall be -15 degrees C or less.
Moreover, about the temperature of a melting | dissolving process, if it is -5 degreeC or more as mentioned above, although the aqueous solution of a cryoprotectant will liquefy, it will be 5 degreeC or more in order to make it liquid reliably. The temperature is preferably 10 ° C. or higher, and particularly preferably about 20 ° C.
本発明の凍結融解試験における凍結融解のサイクル数は、１０サイクル程度とした場合に最も安定した評価ができるので特に望ましいが、より少ないサイクル数で評価できれば、工業的にはより有効である。例えば、３サイクルの場合には、製造条件などによって試験片の粉化（促進劣化）が始まる場合と始まらない場合とがあり、安定した評価が難しいため、５サイクル以上とすることが望ましい。サイクル数の上限は特にないが、評価を短期間に行うために２０サイクル程度を上限とすることが適当である。 The number of cycles of freeze-thaw in the freeze-thaw test of the present invention is particularly desirable because it can be evaluated most stably when it is about 10 cycles, but if it can be evaluated with a smaller number of cycles, it is industrially more effective. For example, in the case of 3 cycles, there are cases where powdering (accelerated deterioration) of the test piece starts or does not start depending on manufacturing conditions and the like, and it is difficult to perform stable evaluation. There is no particular upper limit on the number of cycles, but it is appropriate to set the upper limit to about 20 cycles in order to perform the evaluation in a short time.
本発明の凍結融解試験では、評価を短期間に行うために、凍結工程の時間（但し、温度降下中の時間と保持時間の合計）と融解工程の時間（但し、温度上昇中の時間と保持時間の合計）の合計を１サイクルあたり２４時間以内とすることが好ましい。また、溶液の凝固および融解を安定して試験中に確保するため、凍結工程の時間（但し、温度降下中の時間と保持時間の合計）と融解工程の時間（但し、温度上昇中の時間と保持時間の合計）を、それぞれ１サイクルあたり４時間以上とすることが好ましい。
なお、凍結融解試験におけるサイクル等の試験条件については、ＪＩＳ Ａ１１４８：２０１０「コンクリートの凍結融解試験方法」のＡ法に従う。
In the freeze-thaw test of the present invention, in order to perform the evaluation in a short time, the time of the freezing process (however, the sum of the time during the temperature drop and the holding time) and the time of the thawing process (however, the time during the temperature rise and the holding) The total of time) is preferably within 24 hours per cycle. Also, in order to ensure the solidification and thawing of the solution stably during the test, the time of the freezing process (however, the total of the time during the temperature drop and the holding time) and the time of the thawing process (however, the time during the temperature rise) The total holding time) is preferably 4 hours or more per cycle.
In addition, about test conditions, such as a cycle in a freeze-thaw test, it follows A method of JIS A1148: 2010 "freeze-thaw test method of concrete."
また、試験片を凍結防止剤の水溶液に浸漬させて評価を開始する際に、試験片の内部が水で飽和したものをそのまま凍結防止剤の水溶液に浸漬させても、試験片を一旦乾燥させてから凍結防止剤の水溶液に浸漬させても、評価機関で統一して実施すれば問題はない。ただし、試験片の乾燥度合いによって、溶媒の試験片内部への浸透度合いが変化する可能性があり、データに変動がでる可能性があることから、試験片を乾燥工程を経ることなく凍結防止剤の水溶液に浸漬させること、すなわち、モルタルを養生した後、試験片を凍結防止剤の水溶液に浸漬させるまでの間に乾燥工程を経ないことが好ましい。ここで、乾燥工程には、例えば、風乾、４０℃以上での乾燥処理、常温での長時間放置などが含まれる。 Also, when the evaluation is started by immersing the test piece in an aqueous solution of an antifreeze agent, the test piece is once dried even if the inside of the test piece is saturated with water as it is and immersed in the aqueous solution of the antifreeze agent. Even if it is immersed in an aqueous solution of an anti-freezing agent afterwards, there is no problem if it is carried out in a unified manner by the evaluation organization. However, depending on the degree of drying of the test piece, the degree of penetration of the solvent into the test piece may change, and the data may fluctuate. It is preferable not to pass through a drying process after immersing in the aqueous solution of this, ie, after curing a mortar, and before immersing a test piece in the aqueous solution of a cryoprotectant. Here, the drying process includes, for example, air drying, drying at 40 ° C. or higher, and standing at room temperature for a long time.
本発明では、以上述べたような凍結融解試験後に塊として残存しているモルタルの割合（塊状部の残存率）で、高耐久性コンクリート用骨材としての高炉スラグ細骨材の適性を評価するものであるが、塊として残存しているモルタルの割合（塊状部の残存率）を調べるには、通常、凍結融解試験後のモルタルを所定の篩目の篩で分級し、その篩い上を「塊として残存しているモルタル」とする。そして、この塊として残存しているモルタルの質量を測定し、モルタル（試験片）の全質量に対する割合（塊状部の残存率＝［塊として残存しているモルタルの質量］／［モルタルの全質量］）で、高耐久性コンクリート用骨材としての高炉スラグ細骨材の適性を評価する。 In the present invention, the suitability of the blast furnace slag fine aggregate as an aggregate for highly durable concrete is evaluated by the ratio of the mortar remaining as a lump after the freeze-thaw test as described above (remaining ratio of the lump portion). However, in order to examine the ratio of mortar remaining as a lump (remaining ratio of lump), the mortar after the freeze-thaw test is usually classified with a predetermined sieve mesh, "Mortar remaining as a lump". Then, the mass of the mortar remaining as this lump is measured, and the ratio of the mortar (test piece) to the total mass (remaining ratio of the lump portion = [mass of mortar remaining as a lump] / [total mass of mortar] ]) To evaluate the suitability of blast furnace slag fine aggregate as a highly durable concrete aggregate.
凍結融解試験後のモルタルを分級する際に用いる篩の篩目は０．６〜２．５ｍｍ程度が好ましく、１．２〜２．０ｍｍ程度がより好ましい。篩目が０．６ｍｍ未満では、骨材そのものの平均粒度よりもだいぶ細かいため、試験片が崩れていても篩い下に落ちないケースが多くなる傾向にあり、一方、篩目が２．５ｍｍを超えると、まだ崩壊していないペースト部でも篩い下に落ちるケースがあり、骨材特性の差異が明確になりにくいためである。 The sieve mesh used for classifying the mortar after the freeze-thaw test is preferably about 0.6 to 2.5 mm, and more preferably about 1.2 to 2.0 mm. If the mesh size is less than 0.6 mm, it is much finer than the average particle size of the aggregate itself, so even if the test piece is collapsed, there is a tendency to increase the number of cases where it does not fall under the sieve, while the mesh size is 2.5 mm. If it exceeds, there are cases where the paste portion that has not yet disintegrated falls under the sieve, and the difference in aggregate properties is difficult to be clarified.
製造所やロットが異なる種々の高炉スラグ細骨材を評価対象とし、これらの高炉スラグ細骨材を用いてＪＩＳ Ａ１１４６：２００７の条件でモルタルを作成し、２８日間水中養生を施した。なお、高炉スラグの特性は、高炉スラグを水砕する際の溶融スラグの温度や組成、水砕に用いる水の温度や水圧などの違いにより、異なってくるものと思われる。 Various blast furnace slag fine aggregates with different factories and lots were evaluated, mortar was prepared using these blast furnace slag fine aggregates under the conditions of JIS A1146: 2007, and water curing was performed for 28 days. The characteristics of the blast furnace slag are considered to vary depending on the temperature and composition of the molten slag when the granulated blast furnace slag is granulated, the temperature of the water used for the granulation, and the water pressure.
得られたモルタルを切断して各辺が１０ｍｍの立方体形状の試験片を切り出した。この試験片を３質量％ＮａＣｌ水溶液に浸漬させた状態で、−１８℃の凍結工程と２０℃の融解工程を１サイクルとする凍結融解を５サイクル行う凍結融解試験に供した。また、凍結工程（−１８℃）の時間（但し、温度降下中の時間と保持時間の合計）を１サイクルあたり１６時間、融解工程（２０℃）の時間（但し、温度上昇中の時間と保持時間の合計）を１サイクルあたり８時間とした。凍結融解試験後のモルタル（試験片）を篩目が２ｍｍの篩で分級し、その篩上を塊（塊状部）として残存しているモルタルとし、塊（塊状部）として残存しているモルタルの割合（塊状部の残存率＝（［塊として残存しているモルタルの質量］／［モルタルの全質量］）×１００）を調べた。 The obtained mortar was cut and a cube-shaped test piece having a side of 10 mm was cut out. With this test piece immersed in a 3 mass% NaCl aqueous solution, it was subjected to a freeze-thaw test in which 5 cycles of freeze-thaw were performed with a freezing step at -18 ° C and a thawing step at 20 ° C as one cycle. Also, the freezing step (−18 ° C.) time (however, the total of the time during the temperature drop and the holding time) is 16 hours per cycle, and the time of the melting step (20 ° C.) (however, the time during the temperature rise and holding) The total time) was 8 hours per cycle. The mortar (test piece) after the freeze-thaw test is classified with a sieve having a sieve mesh of 2 mm, the mortar remaining on the sieve as a lump (lumped part), and the mortar remaining as a lump (lumpy part) The ratio (residual ratio of lump portion = ([mass of mortar remaining as a lump] / [total mass of mortar]) × 100) was examined.
同様の高炉スラグ細骨材を用いて、１０ｃｍ×１０ｃｍ×４０ｃｍのコンクリート供試体を成形し、これを３質量％ＮａＣｌ溶液に浸漬した後、凍結融解試験に供した。サイクル等の試験条件については、ＪＩＳ Ａ１１４８：２０１０「コンクリートの凍結融解試験方法」のＡ法で行い、評価としての耐久性指数は、ＪＩＳ Ａ１１４８：２０１０で規定されている相対動弾性係数から求めた。 Using a similar blast furnace slag fine aggregate, a concrete specimen of 10 cm × 10 cm × 40 cm was formed, immersed in a 3% by mass NaCl solution, and then subjected to a freeze-thaw test. The test conditions such as the cycle were performed according to method A of JIS A1148: 2010 “Concrete Freezing and Thawing Test Method”, and the durability index as an evaluation was obtained from the relative dynamic elastic modulus defined in JIS A1148: 2010. .
以上の結果を表１に示す。骨材の最終的な特性は、コンクリートで定まるため、コンクリートの耐久性指数が９０以上のものを“◎”、９０未満７０以上のものを“○”、７０未満６０以上のものを“△”、６０未満のものを“×”とした。
表１によれば、本発明の評価方法による高炉スラグ細骨材の評価結果は、コンクリートの耐久性指数と良く対応しており、本発明の評価方法により、対象とする高炉スラグ細骨材が高耐久性コンクリート用細骨材としての適性を有するか否かを簡便且つ短期間に評価できることが判る。
The results are shown in Table 1. Since the final properties of the aggregate are determined by the concrete, the concrete durability index of 90 or more is “◎”, the less than 90 is 70 or more “O”, and the less than 70 is 60 or more “△”. , Less than 60 was marked "x".
According to Table 1, the evaluation result of the blast furnace slag fine aggregate according to the evaluation method of the present invention corresponds well with the durability index of concrete, and according to the evaluation method of the present invention, the target blast furnace slag fine aggregate is It can be seen that it is possible to evaluate easily and in a short time whether or not it is suitable as a fine aggregate for high durability concrete.
以上のように本発明法によれば、対象とする高炉スラグ細骨材が高耐久性コンクリート用細骨材としての適性を有するか否か、すなわち、当該高炉スラグ細骨材を用いることにより高耐久性コンクリートが得られるか否かを簡便且つ短期間に評価することができる。このため、最適な高炉スラグ細骨材を速やかに選定し、凍結現象やソルトスケーリングが発生しやすい場所に適した高耐久性コンクリートを製造することができる。 As described above, according to the method of the present invention, whether or not the target blast furnace slag fine aggregate has suitability as a high durability concrete fine aggregate, that is, by using the blast furnace slag fine aggregate, Whether durable concrete can be obtained can be evaluated easily and in a short period of time. For this reason, the optimum blast furnace slag fine aggregate can be quickly selected, and highly durable concrete suitable for a place where freezing and salt scaling are likely to occur can be manufactured.
Claims (10)
該試験片を凍結防止剤の水溶液に浸漬させた状態で、−１５℃以下の凍結工程と５℃以上の融解工程を１サイクルとする凍結融解を複数サイクル行う凍結融解試験に供し、該凍結融解試験後に塊として残存しているモルタルの割合から、高耐久性コンクリート用骨材としての当該高炉スラグ細骨材の適性を評価することを特徴とする高耐久性コンクリート用細骨材の評価方法。 A mortar made with blast furnace slag fine aggregate to be evaluated and cured underwater for 7 to 28 days is used as a test piece having a side of 8 to 20 mm in size,
In a state where the test piece is immersed in an aqueous solution of an antifreezing agent, the sample is subjected to a freeze-thaw test in which a freeze-thaw is performed in a plurality of cycles with a freezing step of −15 ° C. or lower and a thawing step of 5 ° C. or higher as one cycle. A method for evaluating a fine aggregate for high durability concrete, characterized by evaluating the suitability of the blast furnace slag fine aggregate as a high durability concrete aggregate from the ratio of mortar remaining as a lump after the test.
該試験片を凍結防止剤の水溶液に浸漬させた状態で、−１５℃以下の凍結工程と５℃以上の融解工程を１サイクルとする凍結融解を複数サイクル行う凍結融解試験に供し、該凍結融解試験後に塊として残存しているモルタルの割合から、高耐久性コンクリート用骨材としての当該高炉スラグ細骨材の適性を評価することを特徴とする高耐久性コンクリート用細骨材の評価方法。 Using a blast furnace slag fine aggregate to be evaluated and steam-cured mortar, a test piece having a side of 8 to 20 mm in size,
In a state where the test piece is immersed in an aqueous solution of an antifreezing agent, the sample is subjected to a freeze-thaw test in which a freeze-thaw is performed in a plurality of cycles with a freezing step of −15 ° C. or lower and a thawing step of 5 ° C. or higher as one cycle. A method for evaluating a fine aggregate for high durability concrete, characterized by evaluating the suitability of the blast furnace slag fine aggregate as a high durability concrete aggregate from the ratio of mortar remaining as a lump after the test.
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